How to test coil and condenser on 1967 Johnson 80hp

I finally ordered a service manual for my motor, but it won't arrive til Monday or Tuesday. I'd like to get some testing done on my coil and condenser in the meantime.

Going to pick up an auto-ranging multi meter tomorrow (shame on me for not having one already)

I'm an electrical noob, so bear with me. Do I check resistance(ohms) to see if they are good? What values should I be looking for in the condenser and coil. Where do I touch the probes on each part?

Re: How to test coil and condenser on 1967 Johnson 80hp

Hate to tell you this but you can check with an ohmmeter to make sure the components are within the specs in the manual but the true test is having a coil/condenser tester to load them for high voltage leaks and ect. Most " Old Time " shops have them.

Re: How to test coil and condenser on 1967 Johnson 80hp

That figures. I don't think I have any "old time" shops anywhere near me. I might as well order a new condenser just to be on the safe side.

I've got 2 coils (one is from my parts motor), so hopefully one or both are good.

Re: How to test coil and condenser on 1967 Johnson 80hp

Coils can go bad--it happened to me. Luckily, I had a spare from a parts motor as well.

Re: How to test coil and condenser on 1967 Johnson 80hp

I'm trying to troubleshoot a possible ignition problem. Would like to be able to test the coil, condenser, points to try and isolate(or rule them out) as a source of the problem.

Re: How to test coil and condenser on 1967 Johnson 80hp

For a quick check on the points-

Use a 12v test light, hook the ground side to the points lead (disconnect it first) and touch the other end to a power source. Remove the plugs and slowly rotate the flywheel (clockwise). The test light should go on and off as the points open and close. This is not a perfect test, but it will quickly tell you if they are working at all.

Quick coil test-

Check resistance with a meter. Primary (small wire to ground) should be very low... just a few tenths of an ohm. Secondary (coil wire to ground) should be approx 1500 ohms. You can also BRIEFLY power up the primary wire and brush the ground lead against a good ground. while doing this, hold the coil wire close to a good ground, you should have a bright blue spark capable of jumping abt a 1/4" gap. This imitates the points opening and closing, and the coil will throw a healthy spark if it's good. Once again, not a perfect test, but it can quickly eliminate some things if you have a bad component.

Re: How to test coil and condenser on 1967 Johnson 80hp

If you have a magneto systems and you follow Seanymphs test, you may burn out your coil.

All you can do is check for cracks in the plastic of the coil. If you see cracks, you need to replace the coil.

Test the coil primary. It should be near a dead short. Test the secondary to one of the primary leads, to make sure it is not open.

There is a rudimentary condenser test, if you have an analog meter. Set the meter to Resistance test. Charge the condenser by putting pos lead on condenser wire and neg lead on condenser body. Needle should deflect for a split second. Now quickly change to low voltage reading on meter and switch meter leads. You should see a small spike of voltage. if so, condenser is good. If not, condenser may be bad or test inclusive.

Re: How to test coil and condenser on 1967 Johnson 80hp

I have a single automotive type (i think) coil. I don't know what you mean by "dead short". I have an auto-ranging multimeter....how do I use it to test the coil? What leads do I put where? And what reading should I be looking for?

I'm a multimeter noob, so be gentle.


I ordered a new condenser and points just to be safe. I've confirmed that the existing points are working already, tho.

On a side note....I checked compression again(because I changed heads/gaskets). It remains 90psi across the board.

Re: How to test coil and condenser on 1967 Johnson 80hp

Very true on the mag. system. Sorry, did not think about that motor possibly being a magneto sys. By "dead short", he means that your resistance test from the small (primary) wire to ground or neg side should result in a very low ohm reading. Meter should read .01 to .05 ohms (roughly)- if it reads much higher than that or if it is open (no reading), then the coil is likely bad (definitely bad if it is open) Primary side coil failures are rare (but do happen), as the actual wire that makes up the windings on that side is fairly heavy, compared to the secondary side. Of course, if there is any cracking or other external breech visible on the coil, throw it away. It is likely corroded internally, and if not failed yet, it will be soon.

Re: How to test coil and condenser on 1967 Johnson 80hp

Bonair, You could probably substitute a standard automotiv coil and condenser for the OMC one, if necessary. It will likely be alot cheaper and work just as well.

I always liked the Ford coil and .25 micfarad condenser pair. It is better to have a matched coil and condenser, BTW.

if you want to go that way go to an auto parts place and find the oldest guy working there, and you can ask him for a Ford Coil and Condenser. if no one is that old, ask for a coil and condenser to fit a '64 Farlane or some other vintage Ford.

You must have the resistance wire on the + side of the coil to reduce the points burning.

Re: How to test coil and condenser on 1967 Johnson 80hp

If I need a coil...I found a guy that has a brand new OEM OMC coil for my motor for $50. I just don't want to start changing parts if I don't need to.

I've got 2 coils right now. One on my boat motor and another on my parts motor. I just wanted to check them both to confirm they are good.

I'm probably going to buy new OEM coil anyway in the week or so, so then I'll be set for quite some time.